Anthony Bourdain, Nigella’s co-star on cooking show The Taste, yesterday blasted her treatment at the hands of the US authorities.

He tweeted: “I am absolutely mortified with embarrassment over the cruelty and hypocrisy of US actions re Nigella travel. Unbelievable.’

(Photo: Channel 4)

And in another blow for the cook, immigration lawyers said it could take up to six or seven months for permission to be granted to return.

Top immigration lawyer Susan McFadden said that Nigella was unlucky to be denied access to the US – but that her drug admissions in court may have counted against her.

She told the Mirror: “One of the questions you have to answer is whether you have ever been convicted of an offence or crime involving moral turpitude or a violation relating to controlled substances.

“If you haven’t been arrested , you can tick no to that.

“But where a person might get in trouble, is that they ask whether you are you a drug abuser or addict.

“It could very well be that someone in the customs and border protection has googled a famous person standing before them and if they see that the person has admitted doing drugs, they may think that this person is still using drugs and is therefore classified as a drug abuser.”

(Photo: BBC)

At the trial of her and ex-husband Charles Saatchi’s personal assistants, who were cleared of fraud, the self-styled “domestic goddess” admitted taking cocaine.

The mother-of-two told jurors she took the class A drug twice - once with her late husband John Diamond when he found out he had terminal cancer and again in 2010 when she claimed she was being “subjected to intimate terrorism” by Mr Saatchi.

But she told the court: “I have never been a drug addict. I’ve never been a habitual user.”

Ms McFadden said that Nigella would now be forced to go to the US Embassy in London for a meeting with a consular officer.

She added: “If the consular officer believes there is reason to suspect drug abuse, they will require that the visa applicant goes to a doctor’s surgery that the embassy has contact with.

“The person has a standard medical and interview. The doctor will then decide whether the person is a drug abuser or not. “

The “standard” medical exam involves a blood test for “a variety of sexually-transmitted infections”, as well as a chest X-Ray.

“Then the doctor will interview the person and then if the doctor believes that drug tests are necessary, he will order they are carried out,” Ms McFadden says.

Yesterday the US embassy in London said Nigella had now been invited to apply for a visa and promised the matter could be “handled routinely and expeditiously”.

A spokeswoman for the US Embassy said: “There are several ways of legally travelling into the United States and Ms Lawson has been invited to come to the Embassy and apply for a visa for travel to the US.

“We understand she has professional requirements for US travel and these matters are generally handled routinely and expeditiously, so stand by.”

The spokeswoman said the embassy was unable to comment on the reasons that someone might be turned away.

An eyewitness said Nigella attempted to board a British Airways flight from London on Sunday morning but was turned away.

“She didn’t seem to say much but she did not look happy,” the onlooker said. “She could not get on the flight so she had to turn around and leave.”

Police reviewed the allegations of drug use which emerged during the trial but Scotland Yard said no further action would be taken.

Nigella visited America earlier this year without any problems to publicise US show The Taste.

She appeared on US TV show Good Morning America to promote her show but also spoke at length about the trial of Elisabetta and Francesca Grillo.

The Grillos had been accused of fraudulently using company credit cards, spending hundreds of thousands of pounds on designer goods for themselves while working as personal assistants to the celebrity couple.

But the Italian sisters claimed every purchase had been approved by their then-bosses and they were found not guilty after jurors deliberated for nine hours.

Ms Lawson told Good Morning America that having details of her acrimonious split from millionaire art dealer Mr Saatchi discussed in court under the glare of the world’s media was “mortifying”.

Yesterday it also emerged that no decision had been made as to whether The Taste would come back either in the US or the UK, where ratings fell to below a million.